He had asthma since he was 2, which meant he coughed ever

since then. Sometimes he coughed badly and sometime OK. Of course every time when the asthma attacked, the steroid cured the asthma, but caused lung function low. In another word, some asthma people can have very high level lung function, while my son only has very low lung function, even though he does not have the asthma attack, his lung function is still very very low, which is why the lung specialist wanted to order the CT scan. I already asked what if CT scan did not show anything, what he is going to do with my son's lung function, and if the method is acceptable, why not just use the new method directly...